It's segregation, I tells ya! SEGREGATION!!

This movie is an excellent place to start out with if you want to make your child feel the frustration, depression, simmering rage and simple out-and-out injustice of being excluded from conveniences or centers of enjoyment merely because you had the bad luck to be born in the "wrong" body. Even by proxy, it all builds and builds in you ( thanks to excellent script pacing ) until, by the time you see the sign at the hospital, you just want to either scream inarticulately or ( as I once did ) snarl, "That's the last ****ing straw!"
If you want to explore this difficult concept further with your child, you could do no better than read William Peters's book "A Class Divided", which originally came out in 1971 ( the year before "Snoopy, Come Home" premiered - and hence may be called its contemporary ). Peters had been instrumental in producing the ABC-TV special "The Eye of the Storm", a documentary illustrating the effects of arbitrary discrimination on a third-grade class in Riceville, Iowa, in February of 1970, by teacher Jane Elliott, who had used this lesson in her class for two years previously ( the first time being the day following the slaying of Martin Luther King, Jr. ). The lesson, which covered two school days and was based on distancing people solely by eye color, demonstrated the appalling quickness with which children can be taught to discriminate, and followed the swings in emotion experienced by the sixteen children as half their number enjoyed the privileges and pleasures of being considered "superior", while the other half had to deal with the strictures imposed on the "inferior".
This daring experiment in teaching brought to Jane Elliott national attention and much more praise and respect than condemnation. Mr. Peters followed up fifteen years later with a second documentary ( also called "A Class Divided" ) for the PBS show "Frontline", with a reunion of Mrs. Elliott and the students who long ago had learned a terrible truth that had clearly affected them deeply indeed. The documentary then proceeded to show Mrs. Elliott as she conducted a workshop with a group of employees of Riceville's Department of Corrections, where all those with blue eyes were made the targets of blatant discrimination / segregation techniques. This second documentary was covered by Mr. Peters in his updated book, "A Class Divided: Then and Now". Both books and documentaries can be obtained easily enough by computer ( check Google for promising sites and entries ).
Though she taught third grade for years, Mrs. Elliott is a first-grade ( by which I mean Grade A ) human being by almost any thoughtful person's standards, mine included. Her story makes an excellent follow-up to the travails of everybody's favorite beagle as he encounters rejection by the Establishment at nearly every turn - even though it does do some good at the end. Inadvertently, of course!